MATRIXSYNTH: Curtis CEM3340 VCO Chips Re-Issued

Friday, June 03, 2016

Curtis CEM3340 VCO Chips Re-Issued

The Curtis CEM3340 VCO has been reissued by Curtis Electromusic. Note the Rev G in the image. That is the new chip. This is pretty big news. If the info below is correct you will be able to order a single chip for $15, or less in bulk.

The CEM3340 was responsible for the main VCO used in quite a few classic synths including the Oberheim OB-Xa, OB-Sx & OB-8, the Voyetra 8, Roland SH-101, MC-202, Jupiter-6, and early model MKS-80, The Sequential Circuits Prophet-5 Rev 3, Prophet-10, Prophet-600, Pro-One, and Prophet T8, Moog Memorymoog, Banana Polysynth, Crumar Spirit, Digisound 80 VCO modules, the Synton Syrinx, Steiner Parker EVI, Doepfer's A-111-1 High End VCO and more.

Image by David Rudolph Smith.

I saw mention that Dave Smith might have been involved with the re-issue. This would make sense as Dave Smith was close to Doug Curtis and DSI uses a later revision of Curtis chips in many DSI synths, however, I checked with DSI and they let me know: “DSI wasn’t involved in the reissue and if anyone would like to find out more about it, they should contact directly.” More info including price follows.

"Founded in 1979, Curtis Electromusic Specialties created a line of signal processing chips for electronic musical instruments and accessories.

Curtis Electromusic currently offers the sought after CEM3340 VCO, a rework of the original design."

And via johnny83 on the Muff Wiggler Forum including contact info, price, and availability.

"Dear all, I've been speaking with onchip for the last 3 months and they have already produced a new batch of CEM 3340. They are available for $15 each! We have tested them and they are revision G and pass our tests on the original Curtis test boards and also various synths we tried them in.

The person to contact is, she has been remarkably helpful and can process your order. Please be aware that revision G has meant the following:

"After reviewing the prior specifications I did decide to change the minimum VCC spec. The old VCC min. was +10V and the new VCC min. is +11V. This is based on my own bench experience with several versions of the device. Many devices will work with a VCC of +10V and others won’t. Devices that won’t work at +10V should easily work at +11V or higher. This is the only specification that we’ve changed" John Borg (Onchip Engineer)

Additionally they have no plans to release the 3310, 3320 and 3360 yet but I think if they see the success of the 3340 it may be apparent the market needs them. I am in communication with them and will continue to push for the other chips to be brought back but to be honest the release of the 3340 is great news as that was the most common curtis chip used.

Here are the price breaks for anyone wanting to get more than a handful:
1 - 499 = $ 15.00
500 - 999 = 12.82
1000 - 4999 = 9.64
5000+ = 7.46

Postage is in addition to this.

I hope you enjoy and spread the word!!"

Update: I don't have official confirmation but I heard they are also re-issuing the CEM3320 filter.  Do a search on 3320 on wikipedia here to see what synths it was used on.


New vs. Old Curtis CEM3340 Rev G Comparison

Published on Jul 4, 2016 Gregory Cox

"This video is a demonstration of the newly manufactured Curtis Electromusic CEM3340 oscillator IC. A comparison is achieved using the Oberheim OB-8 with half of its 3340s replaced and setting the keyboard in dual mode. Voices 1-4 are the original CEM3340s and 5-8 are the Revision Gs. By assigning the same sound to both splits in dual mode, a comparison can be made by fading between both sounds using the program balance knob.

The signal chain is OB-8 / Neutrik patch bay / Apogee Symphony / Headphone Output / Canon 5D mkiii mic input."

This one in via Soviet Space Child.


  1. Hey... that is my cellphone pic... Chips arrived yesterday for a basketcase Memorymoog.
    They appear to operate properly but, if I ever get the Ver 2.4 binary files for the EPROMs I will do more extensive testing... i.e. four-corner temperature/Voltage vs stability/tracking.... currently I am in "lace the harnesses" mode until I can align and test the auto tune circuitry. I opted for 1% Capacitors for the 13 Capacitors replaced in Service Bulletin 840A. They offer less change in capacitance over temperature, I must apologize as I am an electrical Engineer, and not a musician, I will do a report when all of my work is complete... This is only a hobby, I have zero musical talent.

  2. Thank you for posting the pic on Facebook. I'm curious how it turns out. If you can, please let us know.

    1. I finally installed the V2.4 EPROMs in the MM and have 5 of the 18 CEM3340 Rev G VCOs in the first 2 voice cards and there are no noticeable differences in frequency or stability over time.
      This MM I am restoring had nearly every single digital IC fried, but now sounds so Early 80's.

      Sign me, Extremely Satisfied...

      Dave "Not That Dave Smith" Smith

    Dave "Not That Dave Smith" Smith

  4. Jupiter-8 doesn't use CEM3340...!

  5. Thanks! That should have been "Jupiter-6". It's fixed.

  6. I realize I'm responding to an old thread, but wanted to let everyone know that Susan @ OnChip has changed her email to:


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